IRIS stands out from NASA's other missions because it is the first satellite that is designed to continuously study the interface region. The interface region is a scientific puzzle: it makes up the region between the sun's surface – around 6,000 K – and the sun's corona (or upper atmosphere), which tends to fluctuate between 1,000,000 K and 2,000,000 K (though it can spike up to 10,000,000 K during solar storms). From the sun's fusion core moving outward, the temperature steadily declines, as one would expect. Yet after breaching the surface, the temperature spikes again – dramatically. Scientists have some idea of what accounts for this discrepancy, and have had brief success with similar projects, but with IRIS, they hope to improve on the hypotheses by generating consistent and fine-tuned data.